Tear strength, tensile, and softness of sanitary tissue products, for example toilet tissue (bath tissue) products, such as patterned sanitary tissue products, for example sanitary tissue products made on a patterned molding member, are important characteristics to consumers of such sanitary tissue products.
Prior Art FIGS. 1A and 1B show a patterned molding member 10, such as a through-air-drying belt, comprising a plurality of discrete knuckles 12, which are curved discrete knuckles formed by line segments of resin 14 that are arranged in a non-random, repeating pattern, in groups and oriented at an angle α of 45° with respect to the cross-machine direction (CD). In this case, the discrete knuckles 12 are arranged in a woven pattern, for example a herringbone pattern. The discrete knuckles 12 are dispersed within a continuous pillow network 16, which constitutes a deflection conduit into which portions of a sanitary tissue product, such as a fibrous structure ply, being made on the patterned molding member 10 of FIGS. 1A and 1B deflect.
Prior Art FIG. 2 is a MikroCAD image of a resulting sanitary tissue product 18 being made on the patterned molding member 10. The sanitary tissue product 18 comprises a continuous pillow region 20 imparted by the continuous pillow network 16 of the patterned molding member 10 of FIGS. 1A and 1B. The sanitary tissue product 18 further comprises discrete knuckle regions 22 imparted by the discrete knuckles 12 of the patterned molding member 10 of FIGS. 1A and 1B. The continuous pillow region 20 and discrete knuckle regions 22 may exhibit different densities, for example, one or more of the discrete knuckle regions 22 may exhibit a density that is greater than the density of the continuous pillow region 20.
The resulting sanitary tissue product 18 from the patterned molding member 10 of FIGS. 1A and 1B exhibited less than desirable tear and/or tensile properties.
One problem with the known sanitary tissue products is that the known sanitary tissue products, for example toilet tissue (bath tissue) products, exhibit less than desirable tear and/or tensile properties, for example a GM Tear Value as measured according to the Tear Test Method and a GM Tensile Value as measured according to the Dry Tensile Test Method that falls below a line having the following equation: y=0.0122x+18.05 graphed on a plot of GM Tear Value (y-axis) to GM Tensile Value (x-axis) and/or falls below a line having the following equation: y=0.0328x+12.794 graphed on a plot of GM Tear Value (y-axis) to GM Tensile Value (x-axis) and/or falls below a line having the following equation: y=0.0473x+9.179 graphed on a plot of GM Tear Value (y-axis) to GM Tensile Value (x-axis) and/or falls below a line having the following equation: y=0.0654x+4.6601 graphed on a plot of GM Tear Value (y-axis) to GM Tensile Value (x-axis) and/or a GM Tear Value of less than 24.5 g and/or exhibit a GM Tensile Value of greater than 380 g/in and a GM Tear Value of less than 22.7 g and/or a CD Tear Value as measured according to the Tear Strength Test Method and a CD Tensile Value as measured according to the Dry Tensile Test Method such that falls below a line having the following equation: y=0.0188x+16.845 graphed on a plot of CD Tear Value (y-axis) to CD Tensile Value (x-axis) and/or falls below a line having the following equation: y=0.0864x+4.5339 graphed on a plot of CD Tear Value (y-axis) to CD Tensile Value (x-axis) and/or exhibit a CD Tear Value of greater than 26.9 g and/or exhibit a CD Tear Value of less than 26.9 g and/or exhibit a CD Tear Value of less than 23.0 g and/or exhibits a CD Tensile Value of greater than 650 g/in and a CD Tear Value of less than 23.0 g and/or exhibit a CD Tensile Value of greater than 650 g/in and a CD Tear Value of less than 26.9 g and/or exhibit a MD Tear Value as measured according to the Tear Strength Test Method and a MD Tensile Value as measured according to the Dry Tensile Test Method such that the sanitary tissue product falls below a line having the following equation: y=0.0338x+10.235 graphed on a plot of MD Tear Value (y-axis) to MD Tensile Value (x-axis) and/or falls below a line having the following equation: y=0.0716x−0.6674 graphed on a plot of MD Tear Value (y-axis) to MD Tensile Value (x-axis) and/or falls below a line having the following equation: y=0.0716x−0.6674 graphed on a plot of MD Tear Value (y-axis) to MD Tensile Value (x-axis).
Tear Strength, such as GM Tear, CD Tear, and/or MD Tear, is an indication of how well a sanitary tissue product or fibrous structure resists tearing after an initial deformation has been imparted to the sanitary tissue product or fibrous structure. Higher tear strength values exhibited by a sanitary tissue product or fibrous structure tend to be more resilient in a manufacturing setting and also when used by a consumer. Increasing tensile strength is one way to increase tear strength. However, increasing tensile strength is known to decrease softness performance by increasing the stiffness of the sanitary tissue product or fibrous structure. Therefore, it is desirable to have a sanitary tissue product with as high of a tear strength value as possible at as low of a tensile strength value as possible.
In addition, cushiness and flexibility, both characteristics associated with cloths, are attributes that consumers desire in their sanitary tissue products, for example bath tissue products. A technical measure of cushiness is compressibility of the sanitary tissue product which is measured by the Stack Compressibility and Resilient Bulk Test Method. A technical measure of flexibility is plate stiffness of the sanitary tissue product which is measured by the Plate Stiffness Test Method. Current sanitary tissue products fall short of consumers' expectations for cushiness and flexibility.
Accordingly, one problem faced by sanitary tissue product manufacturers is how to improve (i.e., increase) tear properties while at the same time maintaining or improving the compressibility and plate stiffness properties of sanitary tissue products, for example bath tissue products, to make such sanitary tissue products stronger, especially with respect to tear strength, but cushy and flexible sanitary tissue product to better meet consumers' expectations for more clothlike, luxurious, and plush sanitary tissue products.
Accordingly, there exists a need for sanitary tissue products, for example bath tissue products, that exhibit improved tear and/or tensile properties to provide consumers with sanitary tissue products that fulfill their desires and expectations for more comfortable and/or luxurious sanitary tissue products, and methods for making such sanitary tissue products.